Is it possible to have an optional final element in an array?

Question

Is it possible to have an optional final element in an array?

Is there a more graceful way to declare a Typescript array type where the last element is optional?

const example = (arr: [string, string, any | undefined]) => console.log(arr)
example(['foo', 'bar'])

When I call the example(...) function, TypeScript shows the following error message:

Error: Argument of type '[string, string]' is not assignable to parameter of type '[string, string, any]'.
  Property '2' is missing in type '[string, string]' but required in type '[string, string, any]'.(2345)

arrays typescript tuples optional-parameters

Answer 1

Answer №1

function displayOutput(input: [string, string, any?]) {
    console.log(input);
}
displayOutput(['hello', 'world']);

I trust this information proves beneficial.

Answer 2

function displayOutput(input: [string, string, any?]) {
    console.log(input);
}
displayOutput(['hello', 'world']);

I trust this information proves beneficial.

Answer 3

Answer №2

An improved approach could involve implementing generic types to avoid the need for explicitly declaring data types for every element in an array. For example, you can define a function that accepts an array of strings or undefined/null values like so:

const test = (arr: Array<string|undefined|null>) => console.log(arr)
test(['apple', 'banana', ,"pear"])

. This way, you have the flexibility to create arrays containing either strings or null/undefined elements.

Answer 4

An improved approach could involve implementing generic types to avoid the need for explicitly declaring data types for every element in an array. For example, you can define a function that accepts an array of strings or undefined/null values like so:

const test = (arr: Array<string|undefined|null>) => console.log(arr)
test(['apple', 'banana', ,"pear"])

. This way, you have the flexibility to create arrays containing either strings or null/undefined elements.

Is it possible to have an optional final element in an array?

Answer №1

Answer №2

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